Skateboard trucks generally include a hanger that carries an axle, and a baseplate. A pair of wheels are spaced apart at opposite ends of the axle. The hanger is coupled to the baseplate to permit hanger rotation about a pivot axis (the hanger rotation axis), and consequently, turn the skateboard. That is, the “hanger rotation axis” is defined as the pivot axis about which a hanger rotates with respect to its baseplate when change is made to a turn configuration. Conventionally, a pivot end of the hanger is held by a pivot bushing to permit rotation of the pivot end about a first static pivot point. A kingpin and pair of bushings permit rotation of the hanger about a second static pivot point located on the centerline of the kingpin. The first and second pivot points are regarded as “static” because they do not move relative to the base plate. The hanger rotates about a hanger rotation axis defined by the line extending through the first and second static pivot points. The “action angle” in such a conventional truck is defined as the angle between horizontal and the hanger rotation axis for a skateboard supported on a horizontal surface. The hanger rotation axis in that case is identical to an “axle normal axis”, about which axle normal axis the axle moves in pure rotation (in a relative coordinate system) as a change is made in degree or amount of turn.
U.S. utility Pat. No. 8,251,384, to Christensen, et al., and titled “AXLE AND SUSPENSION” discloses an alternative skateboard truck. Embodiments structured according to this patent include an axle hanger that is constrained by a baseplate to oscillate in a single plane as the axle is displaced between maximum left and right turn configurations. The hanger rotates about a dynamic pivot axis, which moves relative to the baseplate. The dynamic pivot axis is defined by a rolling line contact between the hanger and a support surface. The “action angle” of these embodiments is defined as the angle between horizontal and a normal to the aforementioned plane for a skateboard supported on a horizontal surface. The “axle normal axis” of embodiments disclosed in the '384 patent is also normal to the aforementioned single plane, and is parallel to the dynamic pivot axis. The entire disclosure of this '384 patent is hereby incorporated as a portion of the instant disclosure as though set forth herein in its entirety.
One commercially available skateboard truck includes a hard turn stop intended to avoid wheel bite, wherein the board contacts a wheel during a hard turn. This hard turn stop is formed by an interference caused between a pair of set screws and the kingpin shaft. The set screws may be adjusted to determine an allowed amount of deck rotation before they contact the kingpin shaft. A complete description of this skateboard feature may be found on the world wide web at alphaskate.com/innovate/wheelbite.html, the entire disclosure of which is hereby incorporated for its teachings of various characteristics of skateboard trucks.
All known prior art skateboard trucks are structured in such a way that they inherently possess a constant action angle during the entire operation of the truck between maximum left and right turn configurations.